30 
Steam Engine, 
“ a gallon or a gallon ; with a cover that screws on so 
‘‘ accurately as to be steam-tight. In the cover is a hole, 
which may be stopped with a stopper of any kind, as 
of cork or soft wood. This stopper is attached to a 
lever, of which one end is fastened by a joiot or hinge 
to the middle of the cover, and on the other end which 
projects beyond the cover, weights may be hung as on 
the end of a steel-yard. The stopper is kept down by 
a pressure, w'liich is measured by the weight suspended 
at the end of the lever. In this vessel, steam may be 
“ made nearly red-hot. A thermometer graduated to 
400 degrees, or upwards, may be fixed in the cover, 
“ and secured ; but it is not prudent to give a heat beyond 
300 or 350. 
“ When the barometer is about half way between 29 
and 30, the heat of boiling water is indicated by 212 of 
“ Fahrenheit’s thermometer. When the safety valve is 
loaded with one atmosphere, or 141bs. the water will 
‘‘ rise to 240. When, with two atmospheres or 281bs. it 
will raise the mercury to 270 degrees. 
The barometer being as above mentioned, that is, 
about the average weight of the atmosphere, the boiling 
‘‘ point of ether is 98° of Fahrenheit : of ulcoho} of specific 
gravity ,825, 176®; water, 212°; oil of turpentine, 
560° ; linseed oil, 600° ; mercury, 660®. 
‘‘ According to the experiments of Professor Robison, 
a vacuum occasions liquids of whatever kind, to boil 
“ at 145 degrees lower, than they u^ould boil under anat- 
“ mospheric pressure indicated by 30 inches of the baro- 
meter. At this rate, water ought to boil in vacuo at 67® 
Fahrenheit; but Dr, Thompson found the boiling point 
of water under the best vacuum he could make, of 
course not a perfect one, 90 degrees. 
It may be useful to state, that according to Achard^s 
expriments, water saturated with comnion salt is enab- 
